DMD isolation type light path splitting device and ultraviolet imaging row-column intersection detection method

Abstract

This invention discloses a DMD-based isolated optical path splitter, comprising an ultraviolet imaging lens, a dichroic mirror, a digital micromirror device (DMD), an ultraviolet filter, an ultraviolet detector, a visible light camera, a light collector, an optical path shield, and a DMD controller. The invention also discloses an ultraviolet imaging row-column cross-detection method, including the construction of an ultraviolet imaging detection system; a splitter to separate the incident mixed light, an ultraviolet and visible light optical path splitter to further separate the incident mixed light, and an FPGA control module executing a layered strategy of high-precision scanning of global, row, column, and overlapping regions to locate the ultraviolet light region generated by corona discharge and generate an ultraviolet image; the FPGA control module simultaneously acquiring visible light video signals; and the FPGA control module fusing and displaying the visible light video signals and ultraviolet image signals to complete the corona discharge location. This invention solves the problems of delayed corona discharge detection and early warning, high detection equipment cost, and slow imaging speed in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a DMD-based isolated optical path beam splitter, and also to an ultraviolet imaging row-column cross-detection method. Background Technology

[0002] When the voltage on high-voltage equipment and lines rises to a certain level, the air on the surface of the conductor becomes highly ionized, its good insulation properties are destroyed, and it transforms into a conductor, resulting in corona discharge. By detecting the strength of the corona discharge, it is possible to determine whether the high-voltage equipment is in good working condition. Therefore, corona discharge detection is a key means to ensure the normal operation of high-voltage equipment.

[0003] Currently, corona discharge detection mainly employs infrared imaging and ultrasonic detection technologies. However, both technologies suffer from drawbacks such as susceptibility to sunlight interference, difficulty in accurately locating the discharge site, and delayed fault warnings. Furthermore, imported ultraviolet imaging equipment is expensive, hindering widespread application, and traditional ultraviolet imaging uses a line-by-line full-frame scanning method, resulting in slow imaging speeds that cannot meet high-precision detection requirements.

[0004] A digital micromirror device (DMD) is an array of multiple high-speed digital optical reflective switches, composed of numerous small aluminum reflective mirrors. The display resolution is determined by the number of reflective mirrors; one micromirror or an array of micromirrors corresponds to one pixel. By imaging ultraviolet light onto the DMD device, leveraging its pixel-level controllability and high-speed flipping characteristics, and then sequentially scanning each pixel onto an ultraviolet detector, high-speed passive point-scanning ultraviolet imaging can be achieved. This technology holds promise for corona discharge detection, thereby addressing the problems existing in current technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting cross-row and column ultraviolet imaging based on a DMD-isolated optical path splitting device, which solves the problems of delayed corona discharge detection and early warning, high detection equipment cost, and slow imaging speed in the prior art.

[0006] The technical solution adopted in this invention is a DMD-based isolated optical path beam splitter, including an ultraviolet imaging lens, a dichroic mirror, a digital micromirror device (DMD), a first ultraviolet filter, an ultraviolet light detector, a visible light camera, a light collector, an optical path isolation plate, and a second ultraviolet filter; an optical path light shield is provided on the outside of the device. The digital micromirror device (DMD) is electrically connected to a DMD controller.

[0007] The invention is further characterized in that, The ultraviolet imaging lens, dichroic mirror, digital micromirror device and ultraviolet photodetector are arranged in the same plane, and the ultraviolet light path is reflected and deflected in this plane to form a folded light path.

[0008] The reflecting surface of the dichroic mirror faces the digital micromirror device (DMD) and is fixed at a 45° angle relative to the ultraviolet incident light path; the window mirror of the DMD is tilted towards the dichroic mirror and fixed at a 24° angle relative to the incident light path; a visible light camera is positioned on the visible light transmission side of the dichroic mirror; a light collector is positioned opposite the window mirror of the DMD, corresponding to the vertical direction of the window mirror of the DMD; an ultraviolet detector is positioned beside the DMD, with its photosensitive surface facing the reflection and emission direction of the DMD, and the optical axis of the ultraviolet detector is fixed at 72° relative to the incident light direction of the DMD; a first ultraviolet filter is positioned between the DMD and the ultraviolet detector; a second ultraviolet filter is fixed at the light-transmitting window of the optical path isolation plate, located between the dichroic mirror and the DMD. The ultraviolet imaging lens, dichroic mirror, and visible light camera are located in the visible light path area inside the light path shield; the digital micromirror device (DMD), ultraviolet filter, ultraviolet light detector, and light collector are located in the ultraviolet light path area inside the light path shield. An optical path isolation plate is placed between the dichroic mirror and the digital micromirror device (DMD) to serve as a boundary between the visible light path region and the ultraviolet light path region.

[0009] The ultraviolet light detector is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode.

[0010] The transmission wavelength range of both the first and second ultraviolet filters is 220nm to 280nm.

[0011] The ultraviolet light detector has a photosensitive wavelength range of 200nm to 400nm.

[0012] The inner wall of the light path shield is covered with black light-absorbing cloth.

[0013] Each micromirror on the digital micromirror device (DMD) chip is controlled by the DMD controller and has an on state and an off state. When the micromirror is on, ultraviolet light is emitted perpendicularly to the window mirror of the DMD and enters the light collector. When the micromirror is off, ultraviolet light is emitted at a 48° angle to the normal of the window mirror of the DMD and is emitted perpendicularly to the photosensitive surface of the ultraviolet detector after passing through the first ultraviolet filter.

[0014] Another technical solution of the present invention is an ultraviolet imaging row-column cross-detection method, using the above-mentioned DMD-based isolated optical path beam splitter, comprising: Step 1: Set up an ultraviolet imaging detection system; The ultraviolet imaging detection system includes a DMD-based isolated optical path beam splitter, a shaping circuit, an A / D analog-to-digital converter, an FPGA control module, and a display. Step 2: The beam splitter splits the incident mixed light. The FPGA control module executes a layered strategy of high-precision scanning of the global, row block, column block, and overlapping areas to locate the ultraviolet light area generated by the corona discharge and generate an ultraviolet image. Step 3: The FPGA control module synchronously acquires visible light video signals; Step 4: The FPGA control module fuses the visible light video signal and the ultraviolet image signal and displays them to complete the corona discharge location positioning.

[0015] The DMD controller and visible light camera based on the DMD isolated optical path splitter are electrically connected to the FPGA control module; the ultraviolet detector based on the DMD isolated optical path splitter is electrically connected to the shaping circuit; the shaping circuit is connected to the A / D analog-to-digital converter circuit, which is connected to the FPGA control module; the FPGA control module is also electrically connected to the display.

[0016] Step 2 specifically includes the following sub-steps: Step 2.1: The FPGA control module controls all micromirrors of the digital micromirror device (DMD) to be in the off state through the DMD controller, and performs full-domain ultraviolet signal detection through the ultraviolet detector; if an ultraviolet light signal is detected, the subsequent steps are executed; if no ultraviolet light signal is detected, the FPGA control module only outputs the visible light image signal. Step 2.2: The FPGA control module performs row-by-row block detection on the digital micromirror device (DMD). From top to bottom, it sequentially turns off the micromirrors of individual row blocks and turns on the micromirrors of the remaining row blocks, while simultaneously detecting the ultraviolet signal. If the current row block has a valid ultraviolet signal, it is marked as a valid row block. The process of traversing all row blocks is completed. Step 2.3: The FPGA control module performs column-by-column detection on the digital micromirror device (DMD). From left to right, it sequentially turns off the micromirrors of individual columns and turns on the micromirrors of the remaining columns, while simultaneously detecting the ultraviolet signal. If a valid ultraviolet signal exists in the current column, it is marked as a valid column, and the screening of all columns is completed. Step 2.4: Determine the overlapping area as the target area based on the marked valid row blocks and valid column blocks, and perform pixel-by-pixel high-precision scanning imaging only on the target area; the FPGA control module switches the on / off state of the micromirror group corresponding to a single imaging pixel in the target area point by point to complete the independent acquisition of ultraviolet signals in the target area point by point; zero-padding is uniformly applied to the image pixels in non-target areas to finally generate a full frame of ultraviolet light image.

[0017] In step 2.4, each imaging pixel corresponds to a set of pre-arranged DMD microlens groups. The FPGA control module uses the microlens group as the smallest control unit for single-pixel imaging. During the high-precision scanning of the target area, the FPGA control module independently controls the on / off state of the microlens group corresponding to each imaging pixel, so as to realize the independent acquisition of ultraviolet light signals by each pixel and achieve accurate pixel-level imaging.

[0018] The beneficial effects of this invention are: This invention relates to a UV and visible light beam splitting device in a UV imaging row-column cross-detection method based on digital micromirror devices (DMDs). It employs an independent optical path isolation structure, partitioning the UV and visible light paths to prevent overlap and effectively avoid crosstalk between visible light stray light and the UV detection path, reducing detection noise and improving the capture accuracy and signal-to-noise ratio of weak corona discharge UV signals. Simultaneously, the core optical components utilize a coplanar folded optical path layout, resulting in a neat and compact arrangement that effectively reduces the overall size of the device, achieving miniaturization and significantly lowering the difficulty of optical path calibration, component replacement, and on-site debugging. This enhances versatility and maintainability. Furthermore, this invention utilizes a DMD to achieve dynamic and precise gating of the UV beam. Combined with a light collector and a light-absorbing structure, it effectively intercepts and absorbs unwanted stray light, suppressing light scattering and reflection within the cavity, significantly improving optical path transmission stability and imaging quality. This fully meets the high-precision, high-sensitivity, and miniaturized requirements of refined on-site inspection of power equipment.

[0019] This invention relies on FPGA closed-loop feedback iteration to dynamically adjust the working state of the DMD micromirror based on the detection results of the previous frame, intelligently completing partitioned iterative scanning. Compared with the traditional full-domain scanning method, it significantly improves the imaging frame rate and detection speed while ensuring imaging resolution. Combining the precise optical path gating characteristics of the digital micromirror with the high-sensitivity detection advantage of the photomultiplier tube, it can effectively capture weak corona ultraviolet signals, greatly improving the ability to identify and detect micro-discharges under complex working conditions. Attached Figure Description

[0020] Figure 1 This is a structural diagram of the DMD-based isolated optical path splitter in this invention; Figure 2 This is a flowchart of the visible light and ultraviolet light fusion scheme in this invention; Figure 3 This is a flowchart of the ultraviolet imaging multi-layer segmentation iterative algorithm in this invention; Figure 4 This is a schematic diagram of the results of the ultraviolet imaging multi-layer segmentation iterative algorithm in this invention.

[0021] In the figure, 1. Ultraviolet imaging lens; 2. Dichroic mirror; 3. Digital micromirror device (DMD); 4. Light collector; 5. First ultraviolet filter; 6. Ultraviolet light detector; 7. Visible light camera; 8. Optical path isolation plate; 9. Optical path light shield; 10. Second ultraviolet filter; 11. DMD controller. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 This embodiment provides a DMD-based isolated optical path beam splitter, including an ultraviolet imaging lens 1, a dichroic mirror 2, a digital micromirror device (DMD) 3, a first ultraviolet filter 5, an ultraviolet light detector 6, a visible light camera 7, a light collector 4, an optical path isolation plate 8, and a second ultraviolet filter 10; an optical path shield 9 is provided on the outside of the device. The digital micromirror device DMD3 is electrically connected to the DMD controller 11.

[0024] This device achieves coaxial acquisition and separation of visible and ultraviolet light: the incident light from the target is converged by the ultraviolet imaging lens 1 and then illuminates the dichroic mirror 2 at a 45° incident angle. The dichroic mirror 2 reflects the ultraviolet light and transmits the visible light, thus separating the ultraviolet and visible light in space. However, since they both originate from the same incident light path, their geometric distortion characteristics and field of view are highly consistent, facilitating subsequent registration and fusion of visible and ultraviolet light images and avoiding misalignment after fusion.

[0025] Example 2 Based on Example 1, this example further defines the spatial layout and angular parameters of each optical element, such as... Figure 1 As shown, the ultraviolet imaging lens 1, the dichroic mirror 2, the digital micromirror device 3, and the ultraviolet photodetector 6 are arranged in the same plane, and the ultraviolet light path is reflected and redirected in this plane to form a folded light path.

[0026] Specifically: The reflective surface of the dichroic mirror 2 faces the digital micromirror device (DMD3) and is fixed at a 45° angle relative to the ultraviolet incident light path; the window mirror of the DMD3 is tilted towards the dichroic mirror 2 and fixed at a 24° angle relative to the incident light path; the visible light camera 7 is arranged on the visible light transmission side of the dichroic mirror 2; the light collector 4 is arranged on the window mirror face of the DMD3, corresponding to the vertical direction of the window mirror of the DMD3; the ultraviolet detector 6 is arranged beside the DMD3, with its photosensitive surface facing the reflection and emission direction of the DMD3, and the optical axis of the ultraviolet detector 6 is fixed at 72° relative to the incident light direction of the DMD3; the first ultraviolet filter 5 is arranged between the DMD3 and the ultraviolet detector 6; the second ultraviolet filter 10 is fixed at the light-transmitting window of the optical path isolation plate 8, located between the dichroic mirror 2 and the DMD3. The ultraviolet imaging lens 1, the dichroic mirror 2, and the visible light camera 7 are located in the visible light path area inside the light path shield 9; the digital micromirror device (DMD) 3, the ultraviolet filter 5, the ultraviolet light detector 6, and the light collector 4 are located in the ultraviolet light path area inside the light path shield 9. The optical path isolation plate 8 is located between the dichroic mirror 2 and the digital micromirror device DMD3, serving as a boundary between the visible light path region and the ultraviolet light path region.

[0027] Example 3 Based on Example 2, the ultraviolet detector 6 is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode.

[0028] Among them, the ultraviolet photomultiplier tube (UVP) possesses extremely high sensitivity and extremely low noise, enabling it to detect extremely weak (even single-photon level) ultraviolet radiation. Its working principle is as follows: ultraviolet light irradiates the photocathode, generating photoelectrons. These photoelectrons, under the influence of a high-voltage electric field, sequentially bombard multiple dynodes, producing secondary electron emission, ultimately forming an amplified current pulse at the anode. The gain of a UVP can reach 10⁻¹⁰. 5 ~10 7 It is very suitable for weak ultraviolet signal detection scenarios such as corona discharge and flame detection.

[0029] An ultraviolet avalanche photodiode is a photodetector based on the avalanche multiplication effect under reverse bias of a semiconductor PN junction. When ultraviolet photons are absorbed in the depletion region, they generate photogenerated carriers. These carriers undergo collisional ionization in a high electric field region, triggering the avalanche multiplication effect and thus achieving internal gain (typically 10–200). Ultraviolet avalanche photodiodes offer advantages such as small size, low operating voltage (tens to hundreds of volts), fast response speed, and insensitivity to magnetic fields, making them particularly suitable for portable ultraviolet imaging devices with high requirements for size and integration.

[0030] This device can flexibly select an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode as the ultraviolet light detector according to the actual application scenario, such as detection distance, target ultraviolet intensity, system power consumption budget, etc.

[0031] Meanwhile, this embodiment specifies the key parameters of each optical element.

[0032] The first ultraviolet filter 5 and the second ultraviolet filter 10 both have a transmission wavelength range of 220 nm to 280 nm. This band covers most of the ultraviolet characteristic radiation generated by corona discharge and flame combustion. The filters are typically produced using interference coating technology, where high- and low-refractive-index materials (such as HfO2 / SiO2 or Al2O3 / SiO2) are alternately deposited on a substrate such as quartz or calcium fluoride to form a bandpass filter system. Typical performance indicators include: transmittance ≥ 80% at the center wavelength and optical density OD ≥ 4 in the cutoff band (400 nm to 1100 nm), meaning a transmittance of less than 0.01%. This filter effectively suppresses visible and near-infrared stray light from entering the ultraviolet detector, significantly improving the signal-to-noise ratio.

[0033] Specifically, in this embodiment, the second ultraviolet filter 10 is fixed at the light-transmitting window of the optical path isolation plate 8, and its transmission wavelength range is 220nm to 280nm. It can block stray light outside the visible and ultraviolet bands to the maximum extent, ensuring that only ultraviolet signals in the 220nm to 280nm range can enter the ultraviolet optical path region from the visible light path region. This design significantly enhances the isolation effect of the optical path isolation plate 8 and further reduces the interference of residual stray light in the visible light path on the ultraviolet photodetector 6.

[0034] The ultraviolet photodetector 6 has a photosensitive wavelength range of 200nm to 400nm. Whether it is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode, its photocathode material or semiconductor material (such as wide bandgap semiconductors such as SiC, GaN, and AlGaN) has been optimized for this wavelength range to ensure high quantum efficiency (typically ≥30%) in the 200nm to 400nm range, while having extremely low response to visible light longer than 400nm, thus achieving both spectral selectivity and high sensitivity.

[0035] The inner wall of the light-shielding shield 9 is covered with black light-absorbing fabric. This light-absorbing fabric is made of black flocked fabric or black matte velvet material with high absorption and low reflectivity, and its reflectivity in the visible to near-infrared band can be as low as less than 1%. The light-absorbing fabric is tightly attached to the inner wall of the light-shielding shield with double-sided tape or special adhesive, and all seams should be overlapped to avoid exposing the metal wall surface.

[0036] Example 4 Based on Example 3, this example provides a detailed description of the operating state and optical path control mechanism of the digital micromirror device DMD3.

[0037] The Digital Micromirror Device (DMD3) is an array composed of multiple high-speed digital optical reflective switches. It consists of multiple small aluminum reflective mirrors, and the display resolution is determined by the number of reflective mirrors; one micromirror or an array of micromirrors corresponds to one pixel. Each micromirror on the DMD3 chip is controlled by the DMD controller 11 and has an on and off state. In this embodiment, the definition of the operating state of the DMD3 differs from conventional usage: When the micromirror is in the open state, ultraviolet light is emitted perpendicularly to the window mirror of the digital micromirror device DMD3 and enters the light collector 4. The light entering the light collector 4 is useless light, which will interfere with the useful light entering the ultraviolet light detector 6. The light is absorbed by the light-absorbing cloth and the light collector 4 to reduce its scattering and reflection in the ultraviolet light path area.

[0038] When the micromirror is closed, the ultraviolet light is emitted at a 48° angle to the normal of the window mirror of the digital micromirror device DMD3 and then perpendicularly illuminates the photosensitive surface of the ultraviolet detector 6 after passing through the first ultraviolet filter 5, thereby realizing the detection of useful ultraviolet signals.

[0039] This embodiment provides the working principle of a DMD-based isolated optical path splitter, and the overall workflow is as follows: First, the incident light from the target scene (containing both ultraviolet radiation and visible light reflection) enters the ultraviolet imaging lens 1. The ultraviolet imaging lens 1 uses a material with good transmittance for both ultraviolet and visible light (such as fused silica or calcium fluoride) to converge and collimate the incident light, outputting a parallel or nearly parallel incident beam. This beam illuminates the dichroic mirror 2 at a 45° incident angle. The dichroic mirror 2 utilizes its wavelength-selective coating to efficiently reflect ultraviolet light (especially corona discharge characteristic radiation in the 220nm–280nm band) from the incident light (reflectivity ≥95%), while simultaneously efficiently transmitting visible light (400nm–700nm) (transmittance ≥90%). Thus, ultraviolet and visible light are spatially separated for the first time, and because they originate from the same incident light path, they are naturally coaxial, laying an ideal foundation for subsequent image registration and fusion.

[0040] Visible light transmitted through the dichroic mirror 2 directly enters the visible light camera 7, and the visible light camera 7 outputs a visible light image signal.

[0041] The ultraviolet light, after being reflected by the dichroic mirror 2, first passes through the second ultraviolet filter 10 on the optical path isolation plate 8. The second ultraviolet filter 10 effectively blocks any residual stray light that may exist in the visible light path area, achieving physical isolation and spectral purification between the ultraviolet and visible light paths. After passing through the second ultraviolet filter 10, the ultraviolet light enters the ultraviolet light path area and reaches the window mirror of the digital micromirror device (DMD3) along the reflection path.

[0042] The Digital Micromirror Device (DMD3) chip integrates hundreds of thousands to millions of independently controllable micromirrors. Each micromirror, under the control of the DMD controller 11, switches between on and off states at an extremely high frequency. The operating states of the DMD3 are defined as follows: When the micromirror is in the off state (useful light output): the incident ultraviolet light, after reflection, exits at a 48° angle to the normal of the window mirror of the digital micromirror device (DMD3). This outgoing light passes perpendicularly through the first ultraviolet filter 5, further filtering out any residual stray light, and then perpendicularly illuminates the photosensitive surface of the ultraviolet detector 6. The detector converts the ultraviolet light signal into an electrical signal and outputs it.

[0043] When the micromirror is in the open state (no light is excluded): the incident ultraviolet light is reflected and emitted perpendicularly to the window of the digital micromirror device DMD3, directly into the light collector 4.

[0044] The light shield 9, the black light-absorbing cloth on the inner wall, and the light isolation plate 8 of the entire device together provide a working environment with low stray light interference for all the above-mentioned light paths, ensuring that only the target signal light propagates along the designed path throughout the entire optical path from the entrance of the ultraviolet imaging lens 1 to the ultraviolet detector 6 and the visible light camera 7, thereby suppressing background noise to the maximum extent.

[0045] Example 5 This embodiment provides a method for detecting row-column crossover in ultraviolet imaging, using the DMD-based isolated optical path splitter from Embodiment 4, including: Step 1: Set up an ultraviolet imaging detection system; The ultraviolet imaging detection system includes a DMD-based isolated optical path beam splitter, a shaping circuit, an A / D analog-to-digital converter, an FPGA control module, and a display. The DMD controller 9 and visible light camera 7 of the beam splitter are electrically connected to the FPGA control module. The ultraviolet detector 6 of the DMD-based isolated optical path beam splitter is electrically connected to the shaping circuit. The shaping circuit is connected to the A / D converter, which in turn is connected to the FPGA control module. The FPGA control module is also electrically connected to the display. The shaping circuit amplifies, filters, and shapes the weak current pulse signal, converting it into a voltage pulse signal with amplitude and width that meet the input requirements of the A / D converter. The A / D converter converts the analog voltage signal output by the shaping circuit into a digital signal for further processing by the FPGA control module. Both the shaping circuit and the A / D converter are commonly used circuits in the field of ultraviolet light detection. Those skilled in the art can choose commercially available mature chips or conventional discrete components to build the circuit according to actual needs. Their specific internal structures will not be described in detail here.

[0046] Step 2: The beam splitter splits the incident mixed light. The FPGA control module executes a layered strategy of high-precision scanning of the global, row block, column block, and overlapping areas to locate the ultraviolet light area generated by the corona discharge and generate an ultraviolet image. Step 3: The FPGA control module synchronously acquires visible light video signals; Step 4: The FPGA control module fuses the visible light video signal and the ultraviolet image signal and displays them (the visible light and ultraviolet light fusion scheme process is as follows). Figure 2 As shown in the figure, the location of the corona discharge is determined.

[0047] Example 6 This embodiment provides a detailed explanation of the layered scanning strategy executed by the FPGA control module in step 2. Specifically, the FPGA control module uses a layered strategy of high-precision scanning of the global, row blocks, column blocks, and overlapping regions to locate the ultraviolet light region generated by corona discharge and generate an ultraviolet image.

[0048] like Figure 4 As shown, the digital micromirror device (DMD) used in this embodiment has a resolution of 768 rows × 1024 columns, with a total of 32 row blocks, each containing 24 rows, and a total of 32 column blocks, each containing 32 columns. Alternatively, it can be configured with 16 row blocks, each containing 48 rows, and a total of 16 column blocks, each containing 64 columns.

[0049] A single pixel is 3×4 micromirrors in size. For a DMD with a resolution of 768 rows × 1024 columns, the resolution of ultraviolet imaging is 256×256.

[0050] Combination Figure 3 As shown, the FPGA control module executes the layered scanning strategy, which specifically includes the following sub-steps: Step 2.1: The FPGA control module controls all micromirrors of the digital micromirror device DMD3 to be in the off state via the DMD controller, and performs full-domain ultraviolet signal detection via the ultraviolet photodetector 6; if an ultraviolet light signal is detected, the subsequent steps are executed; if no ultraviolet light signal is detected, the FPGA control module only outputs the visible light image signal. For example... Figure 4 As shown, ultraviolet light was detected in the entire area within the red box.

[0051] Step 2.2: The FPGA control module performs row-by-row block detection on the digital micromirror device (DMD3), sequentially turning off individual row block micromirrors and turning on the micromirrors of the remaining row blocks from top to bottom, while simultaneously detecting ultraviolet signals. If a valid ultraviolet signal is present in the current row block, it is marked as a valid row block, and this process is repeated for all row blocks. Figure 4 As shown, ultraviolet light signals were detected in the yellow rows, while no ultraviolet light signals were detected in the other rows.

[0052] Step 2.3: The FPGA control module performs column-by-block detection on the digital micromirror device (DMD3), sequentially turning off individual columns of micromirrors and turning on the micromirrors of the remaining columns from left to right, while simultaneously detecting ultraviolet signals. If a valid ultraviolet signal is present in the current column, it is marked as a valid column, and the screening of all columns is completed. For example... Figure 4 As shown, ultraviolet light signals were detected in the green column blocks, while no ultraviolet light signals were detected in the other column block areas.

[0053] Step 2.4: Determine the overlapping area as the target area based on the marked valid row blocks and valid column blocks, and perform pixel-by-pixel high-precision scanning imaging only on the target area; the FPGA control module switches the on / off state of the micromirror group corresponding to a single imaging pixel in the target area point by point to complete the independent acquisition of ultraviolet signals in the target area point by point; zero-padding is uniformly applied to the image pixels in non-target areas to finally generate a full frame of ultraviolet light image.

[0054] In this system, each imaging pixel corresponds to a set of pre-arranged DMD microlens groups, and the FPGA control module uses the microlens group as the smallest control unit for single-pixel imaging. During the high-precision scanning of the target area, the FPGA control module independently controls the on / off state of the microlens group corresponding to each imaging pixel, so as to realize the independent acquisition of ultraviolet light signals by each pixel and achieve accurate pixel-level imaging.

[0055] by Figure 4Taking step 2.4 as an example, the yellow rows and green columns are marked with ultraviolet light, and the overlapping area of ​​the yellow rows and green columns is marked as the blue area. The blue area is scanned and imaged at the highest resolution. The size of one pixel is 3×4 micromirrors, and the blue area is 24 rows × 32 columns, therefore the blue area has 8×8 pixels. The FPGA control module controls the micromirrors of each pixel in the DMD to be in the off state sequentially from top to bottom and left to right. When all the micromirrors of a certain pixel are in the off state, all the micromirrors of the other pixels in the entire frame are in the on state. When the micromirrors of each pixel are in the off state, the ultraviolet detector collects the ultraviolet light signal and transmits it to the FPGA control module, thus completing the image signal acquisition of one pixel in an ultraviolet light image. The ultraviolet light signals of the 8×8 pixels in the blue area are collected sequentially and transmitted to the FPGA control module. The FPGA control module assigns a value of 0 to the ultraviolet light data of all pixels outside the blue area. At this time, the ultraviolet light signal value of each pixel in the entire ultraviolet light image has been collected.

[0056] This algorithm transforms the full-frame image scanning into scanning imaging of a small area, significantly reducing imaging time and increasing frame rate.

Claims

1. A DMD-based isolated optical path splitter, characterized in that, It includes an ultraviolet imaging lens (1), a dichroic mirror (2), a digital micromirror device (DMD) (3), an ultraviolet filter (5), an ultraviolet light detector (6), a visible light camera (7), and a light collector (4); an optical path shield (8) is provided on the outside of the device. The digital micromirror device (DMD) (3) is electrically connected to a DMD controller (9).

2. The DMD-based isolated optical path splitter according to claim 1, characterized in that, The ultraviolet imaging lens (1), dichroic mirror (2), digital micromirror device (3) and ultraviolet photodetector (6) are arranged in the same plane, and the four are respectively arranged at the four vertices of an approximate rectangle, forming a folded optical path layout.

3. The DMD-based isolated optical path splitter according to claim 2, characterized in that, The ultraviolet imaging lens (1) and the dichroic mirror (2) are arranged diagonally opposite each other along the rectangle; the reflective surface of the dichroic mirror (2) faces the digital micromirror device (DMD) (3) and is fixed at a 45° angle relative to the ultraviolet incident light path; the window mirror of the digital micromirror device (DMD) (3) is tilted towards the dichroic mirror (2) and is fixed at a 24° angle relative to the incident light path; the visible light camera (7) is arranged on the visible light transmission side of the dichroic mirror (2); the light collector (4) is arranged on the side of the digital micromirror device (DMD) (3) and is fixed at a 72° angle to the incident light direction of the digital micromirror device (DMD) (3); the photosensitive surface of the ultraviolet light detector (6) faces the vertical light output direction of the window mirror of the digital micromirror device (DMD) (3); the ultraviolet filter (5) is arranged between the digital micromirror device (DMD) (3) and the ultraviolet light detector (6).

4. The DMD-based isolated optical path splitter according to claim 1, characterized in that, The ultraviolet light detector (6) is an ultraviolet photomultiplier tube or an ultraviolet avalanche photodiode; The ultraviolet filter (5) has a transmission wavelength range of 220nm to 280nm; The ultraviolet photodetector (6) has a photosensitive wavelength range of 200nm to 400nm; The inner wall of the light path shield (8) is covered with black light-absorbing cloth.

5. The DMD-based isolated optical path splitter according to claim 1, characterized in that, Each micromirror on the DMD (3) chip is controlled by the DMD controller (9) and has an open state and a closed state. When the micromirror is open, ultraviolet light is emitted perpendicularly to the window mirror of the DMD (3) and then perpendicularly irradiates the photosensitive surface of the ultraviolet detector (6) after passing through the ultraviolet filter (5). When the micromirror is closed, ultraviolet light is emitted at a 48° angle to the normal of the window mirror of the DMD (3) and enters the light collector (4).

6. A method for detecting row and column crossover in ultraviolet imaging, using the DMD-based isolated optical path splitter as described in any one of claims 1 to 5, characterized in that, include: Step 1: Set up an ultraviolet imaging detection system; The ultraviolet imaging detection system includes a DMD-based isolated optical path beam splitter, a shaping circuit, an A / D analog-to-digital converter, an FPGA control module, and a display. Step 2: The beam splitter splits the incident mixed light. The FPGA control module executes a layered strategy of high-precision scanning of the global, row block, column block, and overlapping areas to locate the ultraviolet light area generated by the corona discharge and generate an ultraviolet image. Step 3: The FPGA control module synchronously acquires visible light video signals; Step 4: The FPGA control module fuses the visible light video signal and the ultraviolet image signal and displays them to complete the corona discharge location positioning.

7. The ultraviolet imaging row-column intersection detection method according to claim 6, characterized in that, The DMD controller (9) and visible light camera (7) based on the DMD isolated optical path splitter are electrically connected to the FPGA control module respectively; the ultraviolet detector (6) based on the DMD isolated optical path splitter is electrically connected to the shaping circuit; the shaping circuit is connected to the A / D analog-to-digital conversion circuit, and the A / D analog-to-digital conversion circuit is connected to the FPGA control module; the FPGA control module is also electrically connected to the display.

8. The ultraviolet imaging row-column intersection detection method according to claim 6, characterized in that, Step 2 specifically includes the following sub-steps: Step 2.1: The FPGA control module controls all micromirrors of the digital micromirror device DMD (3) to be in the off state through the DMD controller, and performs full-domain ultraviolet signal detection through the ultraviolet detector (6); if the ultraviolet light signal is detected, the subsequent steps are executed; if it is not detected, the FPGA control module only outputs the visible light image signal. Step 2.2: The FPGA control module performs row-by-row block detection on the digital micromirror device (DMD) (3), turning off the micromirrors of a single row block and turning on the micromirrors of the remaining row blocks from top to bottom, and simultaneously detecting the ultraviolet signal; if there is a valid ultraviolet signal in the current row block, it is marked as a valid row block, and all row blocks are screened in turn. Step 2.3: The FPGA control module performs column-by-column detection on the digital micromirror device (DMD) (3), turning off the micromirrors of a single column and turning on the micromirrors of the remaining columns from left to right, and simultaneously detecting the ultraviolet signal; if there is a valid ultraviolet signal in the current column, it is marked as a valid column, and all columns are screened in turn. Step 2.4: Determine the overlapping area as the target area based on the marked valid row blocks and valid column blocks, and perform pixel-by-pixel high-precision scanning imaging only on the target area; the FPGA control module switches the on / off state of the micromirror group corresponding to a single imaging pixel in the target area point by point to complete the independent acquisition of ultraviolet signals in the target area point by point; zero-padding is uniformly applied to the image pixels in non-target areas to finally generate a full frame of ultraviolet light image.

9. The ultraviolet imaging row-column intersection detection method according to claim 8, characterized in that, In step 2.4, each imaging pixel corresponds to a set of pre-arranged DMD microlens groups. The FPGA control module uses the microlens group as the smallest control unit for single-pixel imaging. During the high-precision scanning of the target area, the FPGA control module independently controls the on / off state of the microlens group corresponding to each imaging pixel, so as to realize the independent acquisition of ultraviolet light signals by each pixel and achieve accurate pixel-level imaging.

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